Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1149 AM EDT Mon Jun 04 2018 Valid 12Z Thu Jun 07 2018 - 12Z Mon Jun 11 2018 ...Heat to continue for the Desert Southwest to the south-central U.S... ...Pattern overview... Upper ridging is forecast to remain anchored over the southern Plains late this week into next week with troughing on either side of the CONUS. This will maintain well above average temperatures for the southwest and southern Plains (widespread 100s) with daily record max temperatures likely for some areas. A significant trough will attempt to push into the Pacific Northwest late in the period which will introduce cooler than average temperatures to at least Washington/Oregon. The north central and eastern portions of the lower 48 stand the best chance of rain along a wavy frontal boundary as areas of low pressure exit the east. ...Model guidance/predictability evaluation/preferences... The recent GFS/ECMWF runs paired well with the ensemble means with the well-forecast longwave pattern. Differences expanded south of the Gulf of Alaska with the incoming trough next week but a blend among the models/ensembles offered a good starting point. Elsewhere, the UKMET/Canadian offered some corroboration to the GFS/ECMWF to start but otherwise departed from that consensus by about Friday. Smaller scale uncertainties exist within the pattern but most are unresolvable at this lead time (e.g. "ridge rollers" through the Plains). ...Weather highlights and hazards... The heat wave will be the main story with readings 100 degrees plus anywhere from the Desert Southwest eastward along the Mexican border into the state of Texas. Departures from climatology should be around 10 degrees although slightly higher numbers can be found farther north into the remaining Great Plains states and into the Intermountain West/Rocky Mountain chain. Widespread 80s and 90s are likely over these locations (+10 to +15F anomalies). Regarding cool spots, Thursday should prove to be near or slightly below climatology across the East Coast with such conditions persisting into the weekend across Florida given immense cloud cover and rainfall. Elsewhere, deep upper troughing over the Pacific Northwest will hold temperatures around 5 to 10 degrees below average from Saturday onward. It should remain intermittently wet over the southeastern U.S., particularly Florida, given a stagnant upper trough/weakness in conjunction with an anomalous moisture feed. Back toward the middle of the country, multiple convective complexes are likely to erupt north of the ridge with propagation downstream toward the mid-Mississippi Valley and into the Great Lakes/Ohio Valley. SPC has highlighted the Northern Plains on Thursday for some organized severe weather but bouts of heavy rainfall will persist into next week. Elsewhere, it should prove to be quite wet over the Pacific Northwest given the deep cyclonic flow overhead. Strong forcing with the trough and eventual frontal passage could spread considerable early/mid-June precipitation to the region. Fracasso/Rubin-Oster WPC medium range forecasts of 500 mb heights, surface systems, weather grids, quantitative precipitation, and winter weather outlook probabilities can be found at: http://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif http://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif http://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html http://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml http://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4